Control means for vehicle brakes



July 16, 1935. c. A. SAWTELLE CONTROL MEANS FOR VEHICLBBRAKES Filed Feb. 16, 1931 INVENTOR aid/J 63 /Z Jaartedd e ATTORNEY-s ywm wammm Patented July 16, 1935 2, 0

CONTROL MEANS FOR VEHICLE BRAKES Charles A. Sawtelle, Detroit, Mich, assignor, by direct and mesne assignments, to S. and B. Engineering Company, Detroit, Mich., a corporation of Michigan Application February 16, 1931, Serial No. 516,182

Claims. (01. 188196) This invention relates generally to control sills of the frame. The rockshaft I0 is operameans and refers more particularly to improved tively connected to the brakes of the vehicle, means for controlling as well as adjusting vehicle one of which is designated in Figure 1 by the wheel brakes. I reference numeral I2 and as shown is preferably '5" One of the objects of this invention is to proof the internal expanding type having a cir- 5 vide means'operable in dependence upon a precular interior braking surface I3 for engagement determined increase in clearance between the with the brake shoe I4 which is normally spaced relatively movable braking surfaces for adjusta predetermined distance from the brakingsur ing the latter to compensate for wear of the face. As is usually the case, the brake shoes UNITED STATES PATENT. OFFICE,

1o same. are operatively connected to a rockshaft in such Another object of this invention resides in the a manner that rocking movement of thelatter provision of adjusting means operable upon main one direction'effects a movement of the shoes nipulation of the brake control means for auto- 111130 frictional engagement W h the braking matically maintaining a substantially predeter- Surface.

I mined clearance between the relatively movable For rocking the shaft ID to effect an operal5 braking surfaces, I I tion of the brakes, Iprovidetwo separate con- Another advantageous feature of t i trols I5 and IS. The control I5 is in the form tion is to provide control meanscomprising a of a foot actuated pedal C0 y referred t rockshaft operatively connected to the brakes in t e art as a Service brake, while the control and means for adjusting the rotative position I6 is in the form of a lever usually conveniently 20 of the shaft corresponding to brake releasing arranged within; the drivers compartment of the position in dependence upon a predetermined invehicle "for ma pula by t e ha d of t e crease in the clearance between the relatively operator. Asshown particularly in Figure 2, both movable braking surfaces. the controls are connected to the rockshaft in A further object of this invention is to provide such a manner as to opera e latter independa rockshaft of the typespecified operated by a ent of each other. In detail, the means for control element having a lost motion connection independently connecting the controls I5 and I6 therewith permitting rotative adjustment of the to the rockshaft I 0 comprises a pair of tubular same without interfering with the control members I1 and !8 having bifurcated end porelement. I tions I9 respectively pivotally secured-to the con- A still further object of this invention resides trols I5 and IS. The opposite end. portions of in theprovision of'a plurality of separate control the tubular members I! I and I8 telescope a pair elements independently connected to a common of rods 20 and H, respectively, having the rear rockshaft for actuating the same by lost motion ends'pivotally secured as at 22 to a pair of levers connections wherebysaid shaft may be rocked 23 and 24 which in turn are rigidly secured to by either of the control elements without interthe rockshaft -in axial spaced relation. Relative fering with the other. a sliding movement of the telescopically engaging The foregoing as well as other objectswill members is controlled by a suitable clutch 25 be made more apparent as this description promounted within each of the tubular members 401 ceeds, especially when considered in connection I! and I8. As shown particularly in Figure 3,

with the accompanying drawing, wherein: the clutch members 25 are mounted within suit- Figure 1 is a diagrammatic elevational view able slots 26 extending transversely of the tuof a portion of a vehicle brake system; bular' members aforesaid and are formed with Figure 2 is a plan view of my improved brake openings 21 therethrough for receiving the for- 5 control means; I ward end portions of the rods 20. The opposite Figure 3 is a side elevation of the construction side walls 28 of'the slots 26 are flared outwardly shown in Figure 2; and to permit tilting of the clutch members 25 and Figure 4 is a sectional view taken substanthe inner surfaces 29 of the openings 21 in the tially on the line 4--4 of Figure 2. clutch members through which the forward end 59 Referring now more in detail to the drawing, portions of the'rods project, are so fashioned as it will benotedthat there is illustrated diato effect a wedging engagement with the rods grammatically in Figure 1 a portion of a vehicle upon tilting of the clutch members. brake system comprising a rockshaft I I] extend- In the normal position of the controls or in mg transversely of the vehicle frame II and other words, when the brakes are dis-engaged, having the. end portions journaled upon the side the clutch members 25 assume the position shown Assuming that the parts are in the above posi-' tions and the foot pedal I5 is depressed to. apply the brake, it will be noted that depression of the foot pedal causes a pull on the tubular member I! in the direction of the arrow 33. Initial movement of the tubular member I! in the aforesaid direction exerts a pull on the upper end portion of the clutch member 25 and due to the fact that the Spring 3! is tending to maintain the lower portions of the clutch member 25 in engagement. with the stop, it will be apparent that the lower portions of the clutch will have a tendency to v remain stationary causing the clutch to tilt and wedge the clutch surface 29 into locking engagement with the rod 20. As a consequence, continued movement of. the tubular member I! in the direction of the arrow 33 effects a corresponding movement of the rod 20 and since the rod 20 is secured to the rockshaft, the latter will be operated to apply the brakes. It is to be noted, however, that since the rod 2| is also se' cured to the rockshaft, movement of the latter by the rod 20 will also effect a forward movement of the rod 2|, but since the tubular member l8 and associated clutch has not been disturbed from its normal position wherein the latter clutch permits relative sliding movement of the telescoping members, it will be apparent that the rod 2| will be permitted to slide forwardly within the tubular member without interfering with the latteror control lever connected thereto. The reversal of the above function takes place when the hand brake is operated since manipulation of the latter, while causing forward movement of the rod 20 within the tubular member I! does not interfere with the position of the latter and associated clutch 25. Thus, from the foregoing it will be obvious that the two controls function independently of each other for actuating the rockshaft to apply the brakes. As previously stated, it is one of the objects of this invention to provide mechanism for automatically adjusting the brakes upon manipulation of either-of the above controls. The'above adjustment is accomplished by adjusting the rotative position of the rockshaft corresponding to brake releasing position in dependence upon a predeterminedincrease in the clearance between the braking surface and brake band. In detail, a ratchet segment 35 is provided having teeth 36 arranged on a common pitch diameter and having gradually tapered surfaces 3! terminating in shoulders 38. The ratchet segment 35 is provided with a hub 39 sleeved upon the rockshaft II] for rocking movement relative thereto and an arcuate slot 40 of predetermined length is formed in the hub for engaging a pin 4| secured to the rockshaft [0. The arrangement is such as to permit a limited relative movement of'the ratchet segment 35 and the rockshaft 30. 00- operating with the ratchet teeth 36 is a suitable pawl 42 pivotally mounted. intermediate the ends thereof as at 43 to a stationary support and having a shoulder 44 at one end adapted to engage jcuredto a relatively fixed support.

the cooperating shoulders 38 on the teeth 36. The end aforesaid of the pawl is further provided with a cam surface 45 adjacent the shoulder 44 for engaging the cam surfaces 31 of the teeth and is normally held into engagement with the teeth by means of a spring 46 having one end secured to the opposite end of the pawl and the other end secured to a suitable fixed support. i

The rear wall 47 of the slot 40 is normally ,maintained into engagement with the pin by means of a suitable spring 48. having one end secured tothe ratchet and the opposite end se- The construction is such as to permit initial rocking movement of the shaft l0 to apply the brakes by either of the controls without effecting a corresponding rocking movement of the ratchet segment 35'. The length of the slot 40 is so determined as to provide for movement of the ratchet'segment with the rockshaft a sufiicient di'stance'to engage the pawl with the next adjacent tooth on the ratchet when' rocking movement of the shaft to brake applying position exceeds a predetermined amount. In other words, as the brakes become worn, the clearance between the braking surface and shoes increases with the result that a correspondingly greater movement of the rockshaft is necessary to apply the brakes. When the extent of movement of the rockshaft necessary to apply the brakes exceeds the length of the slot 40 and the distance of one tooth space, it will be apparent that the ratchet segment 35 will be rotated relative to the pawlcausing'the cam surface 45 thereof to.

ratchet segment, it will be obvious that the return:

movement of the shaft will be restricted to the length of the slot which corresponds substantially to a predetermined clearance between the shoe and brake flange. In other words, advancing the ratchet one tooth space as stated also advances the brake releasing position of the rockshaft a corresponding'amount and owing to the operative connection between the shaft and brake shoe, the retracted position of the latter will be advanced a similar amount effecting a corresponding reduction in the clearance between the braking surfaces of the drum and shoe. It will further be apparent from the preceding description that owing to the lost motion connections between the controls and rockshaft, rotative adjustment of the latter in the manner stated is accomplished without interfering with the controls.

What I claim as my invention is:

1. In combination, a rockshaft operatively connected to a brake, a plurality of separate controls operatively connected to the rockshaft for actuating the latter independent of each other, and adjusting mechanism associated with the rockshaft and operable upon manipulation of either of said controls for maintaining the brake in a predetermined adjusted position. i

2. In combination, a brake having a braking surface and a member eng-ageable with said surface, a rockshaft operatively connected to the member for actuating the same and mounted for rocking movement to brake applying and brake releasing positions, means for adjusting the rota-" tive position of said shaft corresponding to brake releasing position in dependence upon a predetermined increase in the clearance between the braking surface and member engageable therewith, and means for rocking the shaft including a control element having a lost motion connection therewith permitting adjustment of the same without interfering with the normal position of the control element.

3. In combination, aibrake having a braking surface and a member engageable with said surface, a rockshaft operatively connected to the member for actuating the same and mounted for rocking movement to brake applying and brake releasing positions, means. for adjusting the rotative position of said shaft corresponding to brake releasing position in dependence upon a predetermined increase in the clearance between the braking surface and. member engageable therewith, said means including a ratchet having a lost motion connection with the shaft, a pawl fixed relative to the ratchet and engageable with the teeth on the latter, and a control element for rocking the shaft having a lost motion connection therewith permitting rotative adjustment of the shaft without affecting the position of the control element.

4. In combination, a brake having a braking surface and a member engageable therewith, a rockshaft operatively connected to the member for actuating the same and mounted for rocking movement to brake applying and brake releasing positions, means for adjusting the rotative position of said shaft corresponding to brake releasing position in dependence upon a predetermined increase in the clearance between the braking surface and member engageable therewith, and a plurality of separate controls for independently actuating the rockshaft having lost motion connections with the latter permitting rotative adjustment of the shaft without interfering with the normal positions of the control elements.

5. In a vehicle brake system, the combination with a brake having a braking surface and a member engageable with said surface, of a rockshaft operatively connected to the member for actuating the same and mounted for rocking movement to brake-applying and brake-releasing positions, a control for rocking said shaft means for adjusting the rotative position of said shaft corresponding to brake-releasing position in dependence upon a predetermined increase'in the clearance between the braking surface and member engageable therewith, said means including a ratchet member having a lost motion connection with said rockshaf t permitting relative movement therebetween corresponding in extent to a predetermined desired clearance between the braking surface and member engageable therewith, a pawl fixed relative to the ratchet and successively engageable with the teeth on the latter as the distance between the braking surface and' member engageable therewith increases, and .a connection between said control and rock shaft variable in length in dependence upon the adjustment of the rock shaft to permit said adjustment without interfering with the normal position of the control.

CHARLES A. SAWTELLE. 

